Электродинамические процессы в высоких широтах: материалы междунарордного симпозиума «Полярные геомагнитные явления», 25-31 мая 1986 г., Суздаль, СССР / Междунар. геодез. и геофиз. союз, Междунар. ассоц. геомагнетизма и аэрономии ; Акад. наук СССР, Кол. фил. им. С. М. Кирова, Поляр. геофиз. ин-т ; [редкол.: О. М. Распопов (отв. ред.). и др.]. - Апатиты : Кольский филиал АН СССР, 1988.

130 120 АНіЫЫе (кт ) 110 100 «Ч I £ 3.0 1.0 О иоо 1 к Integzateoi Powez a 1 — 1------------------ 103- I f 02 Hz ----- L. J 1.......1 s f i Z l ___1___1___X. — 1___ »___ ___ i ___ k L j..,— • • t* »"*" * * ... л Ш й Ш к , 3 2 'М 31 Si Time (UT) 32 S i Figure 9. Example of in-situ measurements of the electric field ampli tude and frequency of the unstable waves created b y the modified two stream and the gradient drift plasma instabilities (from Pfaff et al.,1984). The darkest shades correspond to the largest power values. A typical result is shown in Figure 9 w h i c h gives the power and frequency spectra of irregularities as a function of altitude. It reveals that the fluctuations are most intense between about 95 and 115 km and that their f re quencies are generally well below 1 kHz. This is not contradictory to radar results. If the phase velocity of these waves, seen by a 150 MHz radar (STARE k = 2 S V l m ) is close to c0 » 350-400 m/s, their wave frequency would be 350-400 Hz. The wave length spectrum ia difficult to measure w i t h a rocket since spatial fluctuations can either be true wavelength-effects, or can be introduced by the rocket motion. The fact, however, that the irregularities are most intense in the 95 to 115 k m range is in very good agreement wi t h radar measurements. N EW THEORETICAL IDEAS. Recent observations b y N i elsen and Sc h l e g e l (1985)1 that the phase velocities of Farley-Buneman waves in the auroral E-region are always close to the ion acoustic speed cannot be explained w i t h re f er ence to the usual linear theory (i.e.equation 2 ).This result clearly demon strates the need for a new theoretical approach to the Farley-Buneman insta bility. In this section one such n e w approach is outlined, however, before doing so, it will be n e cessary to touch breifly on recent developments in the theory of Farley-Buneman waves in the equatorial E-region where the 85